Quarry subdivision includes controversial septic infrastructure near impaired river
By Jack Reaney SENIOR EDITOR
The second phase of the Quarry subdivision in Big Sky received the green light from Montana Department of Environmental Quality on April 29, with the release of DEQ’s final environmental assessment after more than a year of review since being approved by Gallatin County in April 2024.
The second phase of the Quarry includes the remaining residential lots—45 additional single-family homes as part of the 135-home, 130-apartment subdivision. Activists have long voiced concerns regarding the Quarry’s proposed septic infrastructure due to its proximity to the Gallatin River, an impaired waterway already facing detrimental nutrient loads believed to be related to human infrastructure, especially the septic systems scattered across Big Sky’s canyon area development.
“DEQ appreciates the time and consideration that went into the comments provided on the draft EA,” an April 29 DEQ press release stated. “DEQ prepared the EA in compliance with the Montana Environmental Policy Act and found there are no anticipated significant impacts to the surrounding environment from the proposed drinking water and wastewater facilities.”
The release noted that the four proposed lots would have level-two wastewater treatment, which “can significantly reduce the nitrogen from wastewater prior to treatment by the soils.” As planned, developers will install SepticNET systems, which they argue go “above and beyond” environmental requirements.
The plan is to eventually transition to a central sewer and remove the septic systems.
Conservation group Upper Missouri Waterkeeper previously sued the DEQ for its approval of the Quarry’s first phase. Executive Director Guy Alsentzer reinforced the organization’s views in a recent news release—one week before the EA was released—declaring that the impaired river “no doubt” needs more protection in light of a new study by the Montana Bureau of Mines and Geology.
“The data is clear—septic systems are inappropriate for new development and will worsen the pollution problems impairing the river,” Alsentzer stated. “DEQ and Gallatin County need to recognize the best available science in their respective decision-making processes and require new development to utilize proven, high-quality wastewater treatment options.”
After the EA was released, the Waterkeeper provided a statement via email to Explore Big Sky, noting that the organization is carefully reviewing the EA to ensure its legality and adequacy in preventing pollution and protecting water quality.
The statement noted that the November 2024 draft EA contained legal and scientific deficiencies, many of which are still the subject of the Waterkeeper’s previous lawsuit against the Quarry’s first phase.
“Given the findings of the recent Montana Bureau of Mines and Geology groundwater study confirming the hydrologic connection between groundwater and surface water in the Canyon, the use of septic systems is wholly inappropriate and will exacerbate the nutrient pollution problems that have led to the Gallatin’s impairment,” the Waterkeeper stated.
Local nonprofit Gallatin River Task Force has echoed the Waterkeeper’s argument. In the April 22 news release, GRTF Chief Executive and Science Officer Kristin Gardner discussed an alternative to septic treatment.
“This study reinforces the urgent need for centralized wastewater treatment infrastructure in Gallatin Canyon—a community-driven initiative nearly two decades in the making that has gained meaningful momentum in recent years,” Gardner stated in the release. “Despite the clear benefits to both the Gallatin River and the local drinking water supply, the project continues to face significant challenges. Without it, threats to public health and the environment will only intensify.”
After the EA’s release, Gardner reinforced GRTF’s opposition of any additional septic systems in the canyon.
“[We] would have liked to have seen this project delayed until a centralized wastewater system is in place,” Gardner wrote in a May 1 email to EBS. “We do appreciate the developer going above and beyond the regulations in regard to using the best available septic systems, however, with recurrent algae blooms threatening river and fisheries health, the risk to the river outweighs the need for additional housing.”
Questions surround canyon sewer project
The second phase of the Quarry is now approved for construction. Developer Scott Altman of Big Sky Rock, LLC told EBS that phase one infrastructure is being installed, with plans to begin moving dirt by the end of May. He noted that Big Sky Rock is excited to bring housing to market, and said the Big Sky Community Housing Trust will be a partner in delivering 24 deed-restricted workforce homes.
“Presales of homes will begin this summer, with initial deliveries expected by next spring,” Altman wrote in an email, adding that phase two construction will follow.
Rising costs and engineering snags of building a Gallatin Canyon sewer have posed problems as the Quarry development advances. Engineers with the Big Sky County Water and Sewer District—the local partner that will eventually accept and treat Gallatin Canyon wastewater—and the Gallatin Canyon County Water and Sewer District are facing expensive hurdles in the design process.
Navigating the intersection of U.S. Highway 191 and Montana Highway 64, as well as the narrow Highway 64 corridor, are challenges causing the projected costs of construction to balloon.
The Big Sky Resort Area District will explore public funding mechanisms in the coming year to support the expensive project. If successful, the sewer will diminish long-run environmental concerns of the Quarry project. If costs—and perhaps community voters—prohibit the completion of sewer infrastructure, the Gallatin River may face years of nutrient loading from additional septic systems in a sensitive area of Big Sky.
“While construction costs continue to rise, we remain confident in the long-term value of transitioning to sewer,” wrote Altman, who also serves as board president for the canyon sewer district. “We’ve committed to connect to the canyon sewer system as soon as it becomes operational.”
